A cigarette filter is composed mainly of cellulose acetate fibers. Cellulose acetate fibers are currently manufactured as follows. Specifically, cellulose acetate fibers are obtained in such a manner that a cellulose acetate flake is dissolved in a solvent such as acetone, thus preparing a cellulose acetate spinning solution, after which the spinning solution is fed into a spinning nozzle device and spun in a high-temperature atmosphere using a dry spinning process.
Especially useful as fibers for a cigarette filter, cellulose acetate fibers are appropriately adjusted in fineness so as to facilitate the production of a cigarette filter, and are finally provided in the form of a fiber tow having a crimped band. Then, the cellulose acetate fiber tow is opened by a cigarette filter plug winding device, impregnated with a plasticizer, formed into a rod shape using a filter winding paper, and then cut to a predetermined length, giving a cigarette filter.
Cellulose acetate is obtained by subjecting cellulose to acetic acid esterification, and is inherently biodegradable.
Actually, however, such biodegradable cellulose acetate is not necessarily regarded as good.
For instance, even when cigarette filters made of cellulose acetate fibers are buried in soil, the shape thereof is still maintained for one to two years, and a very long period of time is required to completely biodegrade the cigarette filters buried in soil.
Cigarette filters are assembled in the form of a cigarette product, and thus distributed to consumers and provided for smoking, and finally discarded after smoking. Moreover, cigarette filters may be directly discarded as production waste from cigarette filter manufacturing plants. The cigarette filters thus discarded are collected, and then buried for disposal thereof. In some cases, cigarette filters are uncollected and left in the natural environment. The discarded cigarette filters are problematic because the presence of discarded filters is visually unappealing and also toxicity adsorbed by the used cigarette filters is leached into the environment and may become potentially biohazardous. These problems occur with typical cellulose acetate structures, as well as cigarette filters.
In such situations, a variety of methods of manufacturing a biodegradable filter tow have been proposed, and these methods include using cellulose acetate made of a predetermined biodegradable polymer, an additive for increasing the degradation rate of cellulose acetate, cellulose acetate having a low degree of substitution (DS) to increase biodegradability, and a filter tow material comprising a biodegradable polymer composite such as PHB (poly-hydroxybutyrate)/PVB (polyvinyl butyral) and starch.
However, satisfactory commercial solutions to produce filters which are degraded at sufficiently fast rates so as to overcome disposal problems and are acceptable to consumers have not yet been developed. The biggest limitation of the aforementioned methods is that it is difficult to achieve an acceptable compromise among biodegradation rate, the absorption profile of the filter material, and tobacco flavor characteristics.